Why the internal error was thrown?

com.objectdb.o.InternalException
at com.objectdb.o.CCH.H(CCH.java:298)
at com.objectdb.o.CCH.E(CCH.java:155)
at com.objectdb.o.QRM.Vo(QRM.java:226)
at com.objectdb.o.MST.Vo(MST.java:988)
at com.objectdb.o.WRA.Vo(WRA.java:311)
at com.objectdb.o.WSM.Vo(WSM.java:115)
at com.objectdb.o.QRR.g(QRR.java:247)
at com.objectdb.o.QRR.f(QRR.java:153)
at com.objectdb.jpa.JpaQuery.getResultList(JpaQuery.java:719)

The stack trace indicates an unexpected state of the query result cache, but unfortunately it is unclear how this happened.

We get this exception sporadic in our TestSuite.

We observed this problem on a 32BIT OS.  The same compiled export with enhanced Entites works on our other test machines (64BIT OS).

Maybe help more information to isolate the issue:

[ObjectDB 2.6.8_01] Unexpected exception (Error 990)
Generated by Java HotSpot(TM) Client VM 1.8.0_51 (on Windows 7 6.1).
Please report this error on http://www.objectdb.com/database/issue/new
com.objectdb.o.InternalException: null
com.objectdb.o.InternalException
at com.objectdb.o.CCH.H(CCH.java:298)
at com.objectdb.o.CCH.E(CCH.java:155)
at com.objectdb.o.QRM.Vo(QRM.java:264)
at com.objectdb.o.MST.Vo(MST.java:988)
at com.objectdb.o.WRA.Vo(WRA.java:311)
at com.objectdb.o.WSM.Vo(WSM.java:115)
at com.objectdb.o.QRR.g(QRR.java:247)
at com.objectdb.o.QRR.f(QRR.java:153)
at com.objectdb.jpa.JpaQuery.getResultList(JpaQuery.java:719)
at com.btc.ep.base.dal.internal.services.PersistenceUtilityServiceImpl.getModelElementsByQuery(PersistenceUtilityServiceImpl.java:167)
at com.btc.ep.architecture.dal.impl.ArchitectureRepositoryImpl.findPool(ArchitectureRepositoryImpl.java:699)

The query in findPool:

Collection<PoolImpl> list = persistenceUtilityService
            .getModelElementsByQuery("select distinct m from " + PoolImpl.class.getName() + " m", PoolImpl.class);

The query execution in getModelElementsByQuery:

public <T> List<T> getModelElementsByQuery(String query, Class<T> clazz) {
    EntityManager em = getEntityManager();
    TypedQuery<T> q = em.createQuery(query, clazz);
    q.setHint("objectdb.result-fetch", "LAZY");
    return q.getResultList();
}

Please try build 2.6.8_05 that may fix this exception.